Modifying PAF/Patent design

[EFK]

Some theoretical questions; I'm sure someone must have experimented with some of this and might have some real-world experience. Given a pickup which is unchanged - say a 'plain old' paf or patent pickup - how will adding a thicker magnet of same grade (1/8" A5 to 3/16" A5) change the sound, no other changes being made?

Also, again given no changes, let's say you could drill out the slug holes in one bobbin from 3/16 to 1/4". Not changing anything else - same magnet, same coils etc. - how would this affect sound?

How is a two-slug coils hb different from a typical one w/ polescrews, no other changes being made? I imagine it would be more magnetically efficient?

[David Schwab]

There's lots of examples of modified Gibson style pickups out there.

The screw coil is very inefficient magnetically, and also has lower inductance than the slug coil. There are a lot of double slug designs on the market.. look at DiMarzio's pickups.

Thicker magnets are generally stronger because the pole surface area is larger, so they would probably sound brighter.

Any geometry change will affect the tone, so you'll just have to try them and see.

I like double slugs or blades myself.

[Mike Sulzer]

The screw coil is very inefficient magnetically, and also has lower inductance than the slug coil.

Ever wonder why the screws are longer than the slugs in a PAF type? To make them magnetically pretty close to the slugs, even though the screws are thinner. Remember, this is a humbucker; the slugs and screws need to be similar in magnetic sensitivity in order to cancel hum well. The relevant test is this: Put a PAF type humbucker in strong magnetic hum field; remove the screws one at a time. You can hear the hum get louder as each screw is removed. You need all six screws to get good cancelation; so they must be pretty much like the slugs

Of course the balance is not perfect; you can do better with the types of cores you mentioned so that the two coils are really the same.

[Possum]

...

using a thicker magnet would probably darken the tone because you are adding more metal into the circuit, would boost the midrange probably and clip a little treble off. sometimes you just have to try stuff stuff to know. Big fat slugs has been done before, GFS I believe has a pickup like that and Tom Anderson too.
the original PAF patent design was a double slug pickup, I would think they would be brighter, more single coil sounding, its something I'm going to mess with soon for a special project. theres probably not anything you can think of that hasn't been done before really....

[David Schwab]

Ever wonder why the screws are longer than the slugs in a PAF type? To make them magnetically pretty close to the slugs, even though the screws are thinner.

I think the reason was probably so you had room to raise them. I doubt they put that much thought into it. Also they were probably screws they had on hand. And they still aren't even close to the slugs. And half the field is going out the back which is doing no one any good.

I think everyone here would agree the slug coil is louder.

I was just putting together a humbucker and was messing around with a big neo bar. The pull from the slugs was crazy strong, while the screws were really weak. I could lift the whole pickup with the tip of a thin allen key touching the slugs, but I couldn't lift if with the screws. Unscientific, but a good sign of how much pull is coming from each part.

Welcome back Mike... haven't seen you here or at MIMF in a while.

[David Schwab]

using a thicker magnet would probably darken the tone because you are adding more metal into the circuit, would boost the midrange probably and clip a little treble off. sometimes you just have to try stuff stuff to know.

Oh yeah.. alnico, I was thinking ceramic. D'Oh! Still the thicker magnet is stronger... but you have a good point.

Big fat slugs has been done before, GFS I believe has a pickup like that and Tom Anderson too.
the original PAF patent design was a double slug pickup, I would think they would be brighter, more single coil sounding, its something I'm going to mess with soon for a special project. theres probably not anything you can think of that hasn't been done before really....

I have some Fender humbuckers that have double slugs. I've been planing on rewinding them. I think I like the double slug idea. The JB-ish clone I just wound is too dark for my taste. I like brighter humbuckers.

It's a 50 freakin' year old design... yet people are still coming up with variations.

[Mike Sulzer]

Thanks David; I got booted of MIMF a few months ago after complaining to Deb about personal remarks Charlie Falco made. The stated reasons were:1. taking up too much staff time. 2. not contributing anything to real musical instrument design.

I think the reason was probably so you had room to raise them.

I think there is more to it than that. They are quite a bit longer than they need to be just to give room for raising.

You are right that the slug pulls harder when close to or touching a magnet. There is more magnetic material close to the magnet. But the sensitivity of a pickup coil to external fluctuating fields is more complicated. This involves the changing flux through the coil, the whole thing. A rod of magnetic material amplifies an applied field. The effect is stronger if the rod extends past the ends of the coil, since the flux lines remain straighter.

Anyway, the test I described shows that the sensitivities to hum fields must be pretty close, or the thing would not cancel hum very well, right?

[salvarsan]

Oh yeah.. alnico, I was thinking ceramic. D'Oh! Still the thicker magnet is stronger... but you have a good point.

Try ceramic 8 or partially demagnetized Alnico 8 or A9-HC.

More coercivity --> more treble and dynamics.

-drh

[David Schwab]

Try ceramic 8 or partially demagnetized Alnico 8 or A9-HC.

More coercivity --> more treble and dynamics.

Only because I don't have one laying around... how would that compare to ceramic? I have a bunch of those.

I installed a series parallel switch on my new humbucker.. get's plenty bright in parallel.